1 use crate::sip128::SipHasher128;
2 use rustc_index::bit_set;
4 use smallvec::SmallVec;
5 use std::hash::{BuildHasher, Hash, Hasher};
6 use std::marker::PhantomData;
12 /// When hashing something that ends up affecting properties like symbol names,
13 /// we want these symbol names to be calculated independently of other factors
14 /// like what architecture you're compiling *from*.
16 /// To that end we always convert integers to little-endian format before
17 /// hashing and the architecture dependent `isize` and `usize` types are
18 /// extended to 64 bits if needed.
19 pub struct StableHasher {
23 impl ::std::fmt::Debug for StableHasher {
24 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
25 write!(f, "{:?}", self.state)
29 pub trait StableHasherResult: Sized {
30 fn finish(hasher: StableHasher) -> Self;
35 pub fn new() -> Self {
36 StableHasher { state: SipHasher128::new_with_keys(0, 0) }
40 pub fn finish<W: StableHasherResult>(self) -> W {
45 impl StableHasherResult for u128 {
47 fn finish(hasher: StableHasher) -> Self {
48 let (_0, _1) = hasher.finalize();
49 u128::from(_0) | (u128::from(_1) << 64)
53 impl StableHasherResult for u64 {
55 fn finish(hasher: StableHasher) -> Self {
62 pub fn finalize(self) -> (u64, u64) {
63 self.state.finish128()
67 impl Hasher for StableHasher {
68 fn finish(&self) -> u64 {
69 panic!("use StableHasher::finalize instead");
73 fn write(&mut self, bytes: &[u8]) {
74 self.state.write(bytes);
78 fn write_str(&mut self, s: &str) {
79 self.state.write_str(s);
83 fn write_length_prefix(&mut self, len: usize) {
84 // Our impl for `usize` will extend it if needed.
85 self.write_usize(len);
89 fn write_u8(&mut self, i: u8) {
90 self.state.write_u8(i);
94 fn write_u16(&mut self, i: u16) {
95 self.state.short_write(i.to_le_bytes());
99 fn write_u32(&mut self, i: u32) {
100 self.state.short_write(i.to_le_bytes());
104 fn write_u64(&mut self, i: u64) {
105 self.state.short_write(i.to_le_bytes());
109 fn write_u128(&mut self, i: u128) {
110 self.state.write(&i.to_le_bytes());
114 fn write_usize(&mut self, i: usize) {
115 // Always treat usize as u64 so we get the same results on 32 and 64 bit
116 // platforms. This is important for symbol hashes when cross compiling,
118 self.state.short_write((i as u64).to_le_bytes());
122 fn write_i8(&mut self, i: i8) {
123 self.state.write_i8(i);
127 fn write_i16(&mut self, i: i16) {
128 self.state.short_write((i as u16).to_le_bytes());
132 fn write_i32(&mut self, i: i32) {
133 self.state.short_write((i as u32).to_le_bytes());
137 fn write_i64(&mut self, i: i64) {
138 self.state.short_write((i as u64).to_le_bytes());
142 fn write_i128(&mut self, i: i128) {
143 self.state.write(&(i as u128).to_le_bytes());
147 fn write_isize(&mut self, i: isize) {
148 // Always treat isize as a 64-bit number so we get the same results on 32 and 64 bit
149 // platforms. This is important for symbol hashes when cross compiling,
150 // for example. Sign extending here is preferable as it means that the
151 // same negative number hashes the same on both 32 and 64 bit platforms.
152 let value = i as u64;
157 fn hash_value(state: &mut SipHasher128, value: u64) {
158 state.write_u8(0xFF);
159 state.short_write(value.to_le_bytes());
162 // `isize` values often seem to have a small (positive) numeric value in practice.
163 // To exploit this, if the value is small, we will hash a smaller amount of bytes.
164 // However, we cannot just skip the leading zero bytes, as that would produce the same hash
165 // e.g. if you hash two values that have the same bit pattern when they are swapped.
166 // See https://github.com/rust-lang/rust/pull/93014 for context.
168 // Therefore, we employ the following strategy:
169 // 1) When we encounter a value that fits within a single byte (the most common case), we
170 // hash just that byte. This is the most common case that is being optimized. However, we do
171 // not do this for the value 0xFF, as that is a reserved prefix (a bit like in UTF-8).
172 // 2) When we encounter a larger value, we hash a "marker" 0xFF and then the corresponding
173 // 8 bytes. Since this prefix cannot occur when we hash a single byte, when we hash two
174 // `isize`s that fit within a different amount of bytes, they should always produce a different
175 // byte stream for the hasher.
177 self.state.write_u8(value as u8);
179 hash_value(&mut self.state, value);
184 /// Something that implements `HashStable<CTX>` can be hashed in a way that is
185 /// stable across multiple compilation sessions.
187 /// Note that `HashStable` imposes rather more strict requirements than usual
190 /// - Stable hashes are sometimes used as identifiers. Therefore they must
191 /// conform to the corresponding `PartialEq` implementations:
193 /// - `x == y` implies `hash_stable(x) == hash_stable(y)`, and
194 /// - `x != y` implies `hash_stable(x) != hash_stable(y)`.
196 /// That second condition is usually not required for hash functions
197 /// (e.g. `Hash`). In practice this means that `hash_stable` must feed any
198 /// information into the hasher that a `PartialEq` comparison takes into
199 /// account. See [#49300](https://github.com/rust-lang/rust/issues/49300)
200 /// for an example where violating this invariant has caused trouble in the
203 /// - `hash_stable()` must be independent of the current
204 /// compilation session. E.g. they must not hash memory addresses or other
205 /// things that are "randomly" assigned per compilation session.
207 /// - `hash_stable()` must be independent of the host architecture. The
208 /// `StableHasher` takes care of endianness and `isize`/`usize` platform
210 pub trait HashStable<CTX> {
211 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher);
214 /// Implement this for types that can be turned into stable keys like, for
215 /// example, for DefId that can be converted to a DefPathHash. This is used for
216 /// bringing maps into a predictable order before hashing them.
217 pub trait ToStableHashKey<HCX> {
218 type KeyType: Ord + Sized + HashStable<HCX>;
219 fn to_stable_hash_key(&self, hcx: &HCX) -> Self::KeyType;
222 /// Implement HashStable by just calling `Hash::hash()`.
224 /// **WARNING** This is only valid for types that *really* don't need any context for fingerprinting.
225 /// But it is easy to misuse this macro (see [#96013](https://github.com/rust-lang/rust/issues/96013)
226 /// for examples). Therefore this macro is not exported and should only be used in the limited cases
227 /// here in this module.
229 /// Use `#[derive(HashStable_Generic)]` instead.
230 macro_rules! impl_stable_hash_via_hash {
232 impl<CTX> $crate::stable_hasher::HashStable<CTX> for $t {
234 fn hash_stable(&self, _: &mut CTX, hasher: &mut $crate::stable_hasher::StableHasher) {
235 ::std::hash::Hash::hash(self, hasher);
241 impl_stable_hash_via_hash!(i8);
242 impl_stable_hash_via_hash!(i16);
243 impl_stable_hash_via_hash!(i32);
244 impl_stable_hash_via_hash!(i64);
245 impl_stable_hash_via_hash!(isize);
247 impl_stable_hash_via_hash!(u8);
248 impl_stable_hash_via_hash!(u16);
249 impl_stable_hash_via_hash!(u32);
250 impl_stable_hash_via_hash!(u64);
251 impl_stable_hash_via_hash!(usize);
253 impl_stable_hash_via_hash!(u128);
254 impl_stable_hash_via_hash!(i128);
256 impl_stable_hash_via_hash!(char);
257 impl_stable_hash_via_hash!(());
259 impl<CTX> HashStable<CTX> for ! {
260 fn hash_stable(&self, _ctx: &mut CTX, _hasher: &mut StableHasher) {
265 impl<CTX, T> HashStable<CTX> for PhantomData<T> {
266 fn hash_stable(&self, _ctx: &mut CTX, _hasher: &mut StableHasher) {}
269 impl<CTX> HashStable<CTX> for ::std::num::NonZeroU32 {
271 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
272 self.get().hash_stable(ctx, hasher)
276 impl<CTX> HashStable<CTX> for ::std::num::NonZeroUsize {
278 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
279 self.get().hash_stable(ctx, hasher)
283 impl<CTX> HashStable<CTX> for f32 {
284 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
285 let val: u32 = unsafe { ::std::mem::transmute(*self) };
286 val.hash_stable(ctx, hasher);
290 impl<CTX> HashStable<CTX> for f64 {
291 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
292 let val: u64 = unsafe { ::std::mem::transmute(*self) };
293 val.hash_stable(ctx, hasher);
297 impl<CTX> HashStable<CTX> for ::std::cmp::Ordering {
299 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
300 (*self as i8).hash_stable(ctx, hasher);
304 impl<T1: HashStable<CTX>, CTX> HashStable<CTX> for (T1,) {
306 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
307 let (ref _0,) = *self;
308 _0.hash_stable(ctx, hasher);
312 impl<T1: HashStable<CTX>, T2: HashStable<CTX>, CTX> HashStable<CTX> for (T1, T2) {
313 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
314 let (ref _0, ref _1) = *self;
315 _0.hash_stable(ctx, hasher);
316 _1.hash_stable(ctx, hasher);
320 impl<T1, T2, T3, CTX> HashStable<CTX> for (T1, T2, T3)
326 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
327 let (ref _0, ref _1, ref _2) = *self;
328 _0.hash_stable(ctx, hasher);
329 _1.hash_stable(ctx, hasher);
330 _2.hash_stable(ctx, hasher);
334 impl<T1, T2, T3, T4, CTX> HashStable<CTX> for (T1, T2, T3, T4)
341 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
342 let (ref _0, ref _1, ref _2, ref _3) = *self;
343 _0.hash_stable(ctx, hasher);
344 _1.hash_stable(ctx, hasher);
345 _2.hash_stable(ctx, hasher);
346 _3.hash_stable(ctx, hasher);
350 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] {
351 default fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
352 self.len().hash_stable(ctx, hasher);
354 item.hash_stable(ctx, hasher);
359 impl<CTX> HashStable<CTX> for [u8] {
360 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
361 self.len().hash_stable(ctx, hasher);
366 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
368 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
369 (&self[..]).hash_stable(ctx, hasher);
373 impl<K, V, R, CTX> HashStable<CTX> for indexmap::IndexMap<K, V, R>
375 K: HashStable<CTX> + Eq + Hash,
380 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
381 self.len().hash_stable(ctx, hasher);
383 kv.hash_stable(ctx, hasher);
388 impl<K, R, CTX> HashStable<CTX> for indexmap::IndexSet<K, R>
390 K: HashStable<CTX> + Eq + Hash,
394 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
395 self.len().hash_stable(ctx, hasher);
397 key.hash_stable(ctx, hasher);
402 impl<A, CTX> HashStable<CTX> for SmallVec<[A; 1]>
407 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
408 (&self[..]).hash_stable(ctx, hasher);
412 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for Box<T> {
414 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
415 (**self).hash_stable(ctx, hasher);
419 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for ::std::rc::Rc<T> {
421 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
422 (**self).hash_stable(ctx, hasher);
426 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for ::std::sync::Arc<T> {
428 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
429 (**self).hash_stable(ctx, hasher);
433 impl<CTX> HashStable<CTX> for str {
435 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
436 self.as_bytes().hash_stable(ctx, hasher);
440 impl<CTX> HashStable<CTX> for String {
442 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
443 (&self[..]).hash_stable(hcx, hasher);
447 impl<HCX> ToStableHashKey<HCX> for String {
448 type KeyType = String;
450 fn to_stable_hash_key(&self, _: &HCX) -> Self::KeyType {
455 impl<CTX> HashStable<CTX> for bool {
457 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
458 (if *self { 1u8 } else { 0u8 }).hash_stable(ctx, hasher);
462 impl<T, CTX> HashStable<CTX> for Option<T>
467 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
468 if let Some(ref value) = *self {
469 1u8.hash_stable(ctx, hasher);
470 value.hash_stable(ctx, hasher);
472 0u8.hash_stable(ctx, hasher);
477 impl<T1, T2, CTX> HashStable<CTX> for Result<T1, T2>
483 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
484 mem::discriminant(self).hash_stable(ctx, hasher);
486 Ok(ref x) => x.hash_stable(ctx, hasher),
487 Err(ref x) => x.hash_stable(ctx, hasher),
492 impl<'a, T, CTX> HashStable<CTX> for &'a T
494 T: HashStable<CTX> + ?Sized,
497 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
498 (**self).hash_stable(ctx, hasher);
502 impl<T, CTX> HashStable<CTX> for ::std::mem::Discriminant<T> {
504 fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
505 ::std::hash::Hash::hash(self, hasher);
509 impl<T, CTX> HashStable<CTX> for ::std::ops::RangeInclusive<T>
514 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
515 self.start().hash_stable(ctx, hasher);
516 self.end().hash_stable(ctx, hasher);
520 impl<I: vec::Idx, T, CTX> HashStable<CTX> for vec::IndexVec<I, T>
524 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
525 self.len().hash_stable(ctx, hasher);
527 v.hash_stable(ctx, hasher);
532 impl<I: vec::Idx, CTX> HashStable<CTX> for bit_set::BitSet<I> {
533 fn hash_stable(&self, _ctx: &mut CTX, hasher: &mut StableHasher) {
534 ::std::hash::Hash::hash(self, hasher);
538 impl<R: vec::Idx, C: vec::Idx, CTX> HashStable<CTX> for bit_set::BitMatrix<R, C> {
539 fn hash_stable(&self, _ctx: &mut CTX, hasher: &mut StableHasher) {
540 ::std::hash::Hash::hash(self, hasher);
544 impl<T, CTX> HashStable<CTX> for bit_set::FiniteBitSet<T>
546 T: HashStable<CTX> + bit_set::FiniteBitSetTy,
548 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
549 self.0.hash_stable(hcx, hasher);
553 impl_stable_hash_via_hash!(::std::path::Path);
554 impl_stable_hash_via_hash!(::std::path::PathBuf);
556 impl<K, V, R, HCX> HashStable<HCX> for ::std::collections::HashMap<K, V, R>
558 K: ToStableHashKey<HCX> + Eq,
563 fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
564 stable_hash_reduce(hcx, hasher, self.iter(), self.len(), |hasher, hcx, (key, value)| {
565 let key = key.to_stable_hash_key(hcx);
566 key.hash_stable(hcx, hasher);
567 value.hash_stable(hcx, hasher);
572 impl<K, R, HCX> HashStable<HCX> for ::std::collections::HashSet<K, R>
574 K: ToStableHashKey<HCX> + Eq,
577 fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
578 stable_hash_reduce(hcx, hasher, self.iter(), self.len(), |hasher, hcx, key| {
579 let key = key.to_stable_hash_key(hcx);
580 key.hash_stable(hcx, hasher);
585 impl<K, V, HCX> HashStable<HCX> for ::std::collections::BTreeMap<K, V>
587 K: ToStableHashKey<HCX>,
590 fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
591 stable_hash_reduce(hcx, hasher, self.iter(), self.len(), |hasher, hcx, (key, value)| {
592 let key = key.to_stable_hash_key(hcx);
593 key.hash_stable(hcx, hasher);
594 value.hash_stable(hcx, hasher);
599 impl<K, HCX> HashStable<HCX> for ::std::collections::BTreeSet<K>
601 K: ToStableHashKey<HCX>,
603 fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
604 stable_hash_reduce(hcx, hasher, self.iter(), self.len(), |hasher, hcx, key| {
605 let key = key.to_stable_hash_key(hcx);
606 key.hash_stable(hcx, hasher);
611 fn stable_hash_reduce<HCX, I, C, F>(
613 hasher: &mut StableHasher,
618 C: Iterator<Item = I>,
619 F: Fn(&mut StableHasher, &mut HCX, I),
621 length.hash_stable(hcx, hasher);
625 hash_function(hasher, hcx, collection.next().unwrap());
628 let hash = collection
630 let mut hasher = StableHasher::new();
631 hash_function(&mut hasher, hcx, value);
632 hasher.finish::<u128>()
634 .reduce(|accum, value| accum.wrapping_add(value));
635 hash.hash_stable(hcx, hasher);
640 /// Controls what data we do or do not hash.
641 /// Whenever a `HashStable` implementation caches its
642 /// result, it needs to include `HashingControls` as part
643 /// of the key, to ensure that it does not produce an incorrect
644 /// result (for example, using a `Fingerprint` produced while
645 /// hashing `Span`s when a `Fingerprint` without `Span`s is
647 #[derive(Clone, Hash, Eq, PartialEq, Debug)]
648 pub struct HashingControls {
649 pub hash_spans: bool,